1. Field of the Invention
The present invention relates to a solder ball supplying method and a solder ball supplying device. In particular, the present invention relates to a solder ball supplying method and a solder ball supplying device that are suited for making fine connections, such as connections between a bonding pad that is formed on a magnetic head slider and a pad that is formed on a lead frame side.
2. Description of the Related Art
A connection method is conventionally known, with which electrodes that are objects to be joined are placed close to each other, the electrodes are made to contact ball-shaped solder (hereinafter called solder ball) by using a suctioning jig or the like, and the solder ball is melted, thus making an electrical connection between the electrodes.
A solder ball supplying device that reliably supplies solder balls to the suctioning jig is used in this type of connection method.
FIG. 7 is a structural explanatory diagram that shows a conventional solder ball supplying device.
As shown in FIG. 7, a conventional solder ball supplying device 1 has an upper block 2 and a lower block 3. A ball separator 4 that can slide along a gap between the upper block 2 and the lower block 3 is provided in a location where it is sandwiched by the upper block 2 and the lower block 3.
A hopper 5 that has an opening in an upper surface is provided to the upper block 2. The hopper 5 can store a large number of solder bails 6 with the ball separator 4 used as a bottom surface. Further, an air path 7 that passes through the upper block 2 in a vertical direction is formed in the upper block 2 in the vicinity of the hopper 5.
It is thus possible to supply nitrogen gas that is used to prevent oxidation of the solder balls 6 from a nitrogen supplying means (not shown) provided above the upper block 2 to the air path 7.
A receiving hole 8 that can only take in one of the solder balls 6 is provided in the ball separator 4. The solder balls 6 that freely fall from the hopper 5 go into the receiving hole 8, and the ball separator 4 is made to slide. It is thus possible to convey the solder ball 6 that has gone into the receiving hole 8 to a position directly below the air path 7.
A delivery path 9 that is provided with a diameter that is at least equal to or greater than the outer diameter of the solder balls 6 is provided to the lower block 3, coaxially with the air path 7 formed in the upper block 2. Accordingly, when the ball separator 4 is slid, and the solder ball 6 that has gone into the receiving hole 8 is moved to a position directly below the air path 7, the solder ball 6 is sent through the delivery path 9 to a portion outside of the supplying device by the nitrogen gas that is supplied within the air path 7. The solder ball 6 then moves to a ball receiving pad (not shown) that is formed in an end portion of the delivery path 9. Suctioning is provided to the solder ball 6 by using a suctioning jig or the like, and the solder ball 6 is conveyed to a target joining portion.
It should be noted that ball separators that simply move reciprocatively between the hopper 5 and the air path 7, and those configured by a porous disk are known and may be used as the ball separator 4 described above (refer to JP 2002-25025 A (FIG. 9), and JP 11-509375 A (page 12, lines 18 to 22)).
Further, other configurations of a solder ball supplying device are known. One solder ball supplying device uses a three layer structure consisting of an arrangement mask, a shutter mask, and a supply mask. By sliding the shutter mask that is sandwiched between the arrangement mask and the supply mask, a solder ball freely falls from the arrangement mask side to the supply mask side to be supplied onto a pad (refer to JP 8-236916 A (FIG. 8)). Another device uses an ejector pin that has a suctioning function to push up a hopper, in which a plurality of solder balls are stored, from below to separate out one solder ball from the hopper (refer to JP 7-245473 A, FIG. 4 and FIG. 6, for example).
However, problems such as those described below exist with the solder ball supplying devices mentioned above.
That is, with the connection method that uses a solder ball, the outer diameter of the solder ball becomes smaller with miniaturization of an object to be joined. Accordingly, if the solder balls themselves are charged with static electricity, there is a problem in that the solder ball cannot be reliably supplied with a method (the so-called free fall method) in which each solder ball is separated out by its own weight, because separation characteristics between the balls worsen due to the reduced weight of the solder balls.
Further, the separation characteristics of the solder balls worsen also when using the method of pushing up and separating a solder ball from a hopper, in which a large number of solder balls are stored, by using an ejector pin. Accordingly, other solder balls are connected to the solder ball that is pushed up, taking on the shape of a bunch of grapes. A problem exists in that it is difficult to extract a single solder ball.
With the solder ball supplying device 1 described above, the solder ball 6 may rub against a block side, causing a jam in a device main body, if the solder ball 6 is not completely received within the receiving hole 8. Disassembly work to remove the upper block 2 becomes necessary in order to remove the solder ball 6 from the receiving hole 8, and this is difficult from the viewpoint of maintenance.